NO. 1 TAYLOR: PACIFIC MARINE ALGAE 177 



KEY TO SPECIES 



1. Plants with terete erect branches 2 



1. Plants showing an extensive basal layer, crustose or bracketlike, 

 to 3-5 mm thick and sometimes several centimeters in diameter, 

 eventually bearing erect platelike extensions to 3 cm tall, 1.3-1.7 

 mm thick, which join marginally to form a chambered plant with 

 cavities 3-20 mm diam. ; conceptacles numerous, but slightly ele- 

 vated, 450-570 fi diam., formed on both the horizontal and the 

 erect portions of the plant L. Farlowii 



2. Plants remaining attached 3 



2. Plants becoming free, the basal crust thin, to about 450 fi thick, 

 enclosing a hard object, bearing short erect divaricate cylindrical 

 branches to 3 mm diam., 3-7 mm long, with somewhat expanded 

 ends; medullary cells 3-10 fx long, 2-7 /x diam.; conceptacles in 

 the ends of the branches, little elevated, 700-950 fi diam. . . 

 L. divaricatum 



3. Erect branches relatively tall, redivided 4 



3. Basal crust thin, about 0.2 mm thick, bearing erect slender 

 branches 0.5-0.75 mm diam., 8 mm tall, or somewhat more if 

 branched, the ends often a little swollen; medullary cells of the 

 branches 7-12, rarely to 20 fx long, 3-9 fi diam. . . L. bracchiatum 



4. Branches commonly much exceeding 2 mm diam. L. amplostratum 



4. Branches generally less than 2 mm diam 5 



5. Medullary cells forming alternate wide and narrow zones . . 

 L. moluccense v. geminostratum 



5. Medullary zones not of contrasting widths 6 



6. Basal crust bearing crowded erect branches 1-2 mm diam., 5-20 

 mm tall, repeatedly divided and anastomosing; medullary cells 

 20-35 fj. long; perithallic cells 10-15 fi long; in the f. galapagense 

 the medullary cells reported to be 27-60 /i long, the perithallic 

 cells 11-22 /A L. frutescens f. galapagense 



6. Basal crust bearing smooth erect anastomosed branches about 1 

 mm diam., repeatedly divided, 5-20 mm tall, the ends rather 

 truncate; medullary cells 20-40 /t long; conceptacles to 450-500 

 fjL in internal, 800 /x in external diameter . . . L. trichotomum 



Lithophyllum Farlowii Heydrich 

 Plates 39-42 

 Heydrich 1901a, p. 532, pi. 11, fig. 6; 1901b, p. 420 (as L. claudes- 

 cens) ; Lemoine 1929, p. 61, pi. 1, fig. 3, pi. 2, fig. 5 (as L. claudescens) ; 

 Setchell & Mason 1943, p. 95. 



